Electron discharge tube



June 19, 1951 N. WARMOLTZ ELECTRON DISCHARGE TUBE Y Filed July 28, 1949INVENTOR.

AGE/V7 Patented June 19, 1951 UNE'EED STATES PATENT ELECTRON DISCHARGETUBE Application July 28, 1949, Serial No. 107,257 In the NetherlandsSeptember 30, 1948 ii-Claims. 1

This invention relates to devices comprising an electric discharge tubehaving a mercury cathode and an ignition electrode arranged over theoathode surface which initiates the discharge by a high voltage appliedthereto.

In order to ensure ignition in devices of the aforesaid kind, highvoltages are required, since in view of variations in the level of thecathode, inter alia due to capillary waves, the distance betweenignition electrode and cathode surface must be comparatively large.

It is known to bring about ignition by splashing the ignition electrodearranged over the cathode surface with cathode liquid by agitating thelatter or by moving the ignition electrode towards the cathode surfaceby electrostriction. Since the ignition is effected in such devices byinterrupting a current between a solid electrode and a liquid cathode,material soiling is liable to occur. Furthermore, the devices foragitating the cathode liquid or the ignition electrode itself arecomparatively complicated.

According to the present invention, in devices comprising an electricdischarge tube having a mercury cathode and an ignition electrodearranged over the cathode surface and to which a high voltage is appliedto ensure ignition, the surface of the cathode is set into vibration.This ensures that waves and sharp points are produced on the cathodesurface, resulting locally in an increased field strength betweencathode and ignition electrode. Thus, the ignition may be produced byconsiderably lower voltages across the ignition electrode than in thecase of a smooth cathode-surface.

The frequency of the vibrations of the cathode surface is preferablychosen to be at least ten times the required frequency of the discharge,in order to ensure that the ignition takes place a very short time afterthe application of the ignition voltage. The surface of the cathode maybe set into vibration by immersing in the cathode liquid an elementwhich is deformed under the action of magnetostriction, 01' the elementmay be coupled to an ultrasonic generator.

In order that the invention may be more clearly understood and readilycarried into effect, one example will now be described with reference tothe accompanying drawing, which shows a liquid cathode electricdischarge tube having a vibratory element immersed in the cathodeliquid.

In the accompanying drawing, the discharge tube has a glass envelope I,a mercury cathode 2 and a graphite anode 3.

An ignition electrode 4 is provided at a distance of a few millimetresfrom the cathode 2. A nickel tube 5 is immersed in the cathode 2 and issurrounded by an insulated coil through which a current of the desiredfrequency may be supplied, with the result that the nickel tube exhibitsmagnetostriction in the direction of its length and the surface of thecathode is set into vibration. The ripple effect may be produced eitherat the desired moment of ignition, after a voltage has been applied tothe electrode, or there may be a continuous ripple effect produced inwhich event a voltage pulse is supplied to the ignition electrode at thedesired moment of ignition.

What I claim is:

1. A device comprising an electric discharge tube having an envelope, ananode electrode positioned within said envelope, a liquid mercurycathode spaced from said anode electrode within said envelope and havinga surface portion of given level facing said anode, means to produceripples at said surface of'said liquid cathode to vary said surfacelevel above and below said given level, and an ignition electrode spacedfrom the given surface level of said liquid cathode at a distancegreater than the height of said ripples whereby on application of avoltage between the said ignition electrode and the said cathode adischarge occurs between said ignition electrode and cathode and tubeignition is effected.

2. A device comprising an electric discharge tube having a givendischarge frequency, said tube having an envelope, an anode electrodepositioned within said envelope, 2. liquid mercury cathode spaced fromsaid anode electrode within said envelope and having a surface portionof given level facing said anode, means to produce ripples of afrequency substantially ten times that of said discharge frequency atsaid surface of said liquid cathode to vary said surface level above andbelow said given level, and an ignition electrode spaced from the givensurface level of said liquid cathode at a distance greater than theheight of said ripples whereby on application of a voltage between thesaid ignition electrode and the said cathode a discharge occurs betweensaid ignition electrode and said cathode and tube ignition is effected.

3. A device comprising an electric discharge tube having an envelope, ananode positioned within said envelope, a liquid mercury cathode spacedfrom said anode within said envelope and having a surface portion ofgiven level facing said anode, magnetostriction means to produce ripplesat said surface of said liquid cathode to vary said surface level aboveand below said given level, and an ignition electrode spaced from thegiven surface level of said liquid cathode at a distance greater thanthe height of said ripples whereby on application of a voltage betweenthe said ignition electrode and the said cathode a discharge occursbetween said ignition electrode and said cathode and tube ignition iseffected.

4. A device comprising an electric discharge tube having an envelope, ananode positioned within said envelope, a liquid mercury cathode spacedfrom said anode within said envelope and having a surface portion of agiven level facing said anode, a magnetostrictive element and an excitertherefor within said liquid cathode to produce ripples at said surfaceof said liquid cathode to vary said surface level above and below saidgiven level, and an ignition electrode spaced from the given surfacelevel of said liquid cathode 4 at a distance greater than the height ofsaid ripples whereby on application of a voltage between the saidignition electrode and the said cathode a discharge occurs between saidignition electrode and said cathode and tube ignition is effected.

NICOLAAS WARMOLTZ.

REFERENCES CITED The following references are of record in the .file ofthis patent:

UNITED STATES PATENTS Great Britain Nov. 5, 1931

